A hybrid power system for a harbor tug

Abstract

The application relates to the field of ship power technology and discloses a harbor tug hybrid power system, which comprises an engine and a Z-shaped propeller, the engine power output end is connected with a gear box, the gear box is internally provided with a clutch, the gear box output shaft one end is connected with the Z-shaped propeller, the engine output shaft one side is provided with a P1 generator, the gear box output shaft one end is provided with a P2 motor, the P1 generator is electrically connected with a direct current network, the direct current network is electrically connected with a battery pack and an inverter, and the inverter is electrically connected with a ship power grid. According to the characteristics of the harbor tug operation condition, the system is operated in the pure electricity or series hybrid mode under the low load condition, only one diesel engine is needed as the main generator set gap operation. Under the medium and high load conditions, the diesel engine is directly driven in the mode, the transmission efficiency is high, the energy conversion loss is small, the engine can be operated in the high-efficiency and low-oil-consumption condition all the time, and the fuel consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of marine propulsion technology, specifically to a hybrid power system for harbor tugboats. Background Technology

[0002] Azimuth-turning harbor tugboats are primarily used to assist other vessels in port operations such as pushing, towing, and shifting. They are small in size but have powerful main engines, capable of towing vessels dozens of times their own size, and their operating conditions are relatively complex. Traditional harbor tugboats use two high-powered diesel engines on either side, connected by universal joints to two Z-type propellers at the stern for direct propulsion. In operation, 20% of the time the tugboat is idle with the clutch disengaged and the engine idling without outputting power; 40% of the time the engine operates at its lowest load, outputting only 18% of its rated power; 30% of the time the engine operates at medium load, outputting 30% of its rated power; and only 10% of the time the engine operates at a high load, outputting 50%-100% of its rated power.

[0003] Diesel engines suffer from low fuel combustion efficiency and severe carbon buildup in the combustion chamber under prolonged low-load conditions, easily emitting blue smoke. Under sudden load increases, incomplete fuel combustion leads to the emission of black smoke. Therefore, port tugboats face increasingly urgent requirements for emission reduction and energy conservation, while also needing to maintain continuous operation and endurance, necessitating innovative upgrades to their power systems and equipment. Summary of the Invention

[0004] The purpose of this invention is to provide a hybrid power system for port tugboats to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a hybrid power system for port tugboats, comprising an engine and a Z-type propeller, wherein a gearbox is connected to the power output end of the engine, a clutch is provided inside the gearbox, one end of the output shaft of the gearbox is connected to the Z-type propeller, a P1 generator is provided on one side of the output shaft of the engine, a P2 motor is provided on one end of the output shaft of the gearbox, the P1 generator is electrically connected to a DC grid, the DC grid is electrically connected to a battery pack and an inverter, the inverter is electrically connected to a ship's electrical grid, and the ship's electrical grid is electrically connected to the P2 motor.

[0006] As a further explanation of the present invention, the P1 generator includes a left P1 generator and a right P1 generator. One end of the input shaft of the left P1 generator is connected to one side of the engine output shaft by gear meshing, and one end of the input shaft of the right P1 generator is connected to one side of the engine output shaft by gear meshing.

[0007] As a further explanation of the present invention, the P2 motor includes a left P2 motor and a right P2 motor. One end of the output shaft of the left P2 motor is connected to one end of the output shaft of the gearbox through gear meshing, and one end of the output shaft of the right P2 motor is connected to one end of the output shaft of the gearbox through gear meshing.

[0008] As a further illustration of the present invention, it includes: pure electric power mode, hybrid power mode and direct drive mode.

[0009] As a further explanation of the present invention, in the pure electric power mode, power is drawn from the DC grid to drive the output shafts of the left P2 motor and the right P2 motor to rotate, thereby driving the Z-type thruster to rotate.

[0010] As a further explanation of the present invention, in the direct drive mode, the engine output shaft drives the gearbox input shaft to rotate, and the gearbox output shaft drives the Z-type propeller to rotate.

[0011] As a further explanation of the present invention, in the hybrid mode, the engine starts, which drives the output shaft to drive the left P1 generator and the right P1 generator to generate electricity, which supplies power to the left P2 motor and the right P2 motor, and the excess electrical energy is used to charge the battery pack.

[0012] As a further explanation of the present invention, the inverter is a three-phase AC inverter, which is used to convert the DC power from the DC grid into three-phase AC power, and connect to the ship's power grid to provide power for the tugboat's navigation, control, winch, and lighting auxiliary equipment.

[0013] As a further explanation of the present invention, there are two engines, one of which serves as the main generator set and the other as the direct drive unit. The rated power of the P1 generator is 50%-60% of the rated power of the engine, and the maximum power of the P2 motor is 50%-60% of the rated power of the engine.

[0014] As a further explanation of the present invention, the battery pack is a lithium-ion battery pack.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] This invention utilizes an engine and a P1 generator. In hybrid mode, the P2 motor is powered while the battery pack is charged. In direct-drive mode, the engine's surplus power supplies the DC grid, and the battery pack provides additional power. The P2 motor drives the Z-shaped propeller in both pure electric and hybrid modes. In direct-drive mode, when the tugboat needs acceleration, the engine and motor work together, effectively solving the problem of black smoke caused by sudden load changes during conventional tugboat operations. Compared to conventional hybrid and pure electric propulsion systems, this system eliminates the need for high-power generators and drive motors. The generators and drive motors are smaller, smaller, and less expensive, making it suitable for replacing and retrofitting traditional tugboats. This system is designed for the characteristics of port tugboat operations. Under low load conditions, in pure electric or series hybrid mode, only one diesel engine is needed as the main generator set for intermittent operation. Under medium and high load conditions, the diesel engine's direct-drive mode offers high transmission efficiency and low energy conversion loss, allowing the engine to operate continuously in a highly efficient and fuel-efficient manner, reducing fuel consumption. Attached Figure Description

[0017] Figure 1 This is an example diagram illustrating the working principle of a hybrid power system for port tugboats according to the present invention;

[0018] Figure 2 This is an energy flow diagram of a hybrid power system for a harbor tugboat according to the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Please see Figures 1-2 This invention provides a technical solution: a hybrid power system for port tugboats, comprising an engine and a Z-type propeller. The engine's power output end is connected to a gearbox, and a clutch is provided inside the gearbox. One end of the gearbox's output shaft is connected to the Z-type propeller. A P1 generator is provided on one side of the engine's output shaft, and a P2 motor is provided on one end of the gearbox's output shaft. The P1 generator is electrically connected to a DC grid, and the DC grid is electrically connected to a battery pack and an inverter. The inverter is electrically connected to a ship's electrical grid, and the ship's electrical grid is electrically connected to the P2 motor.

[0021] This system is equipped with a small-capacity battery pack, and tugboat port operations primarily utilize a hybrid mode. Compared to traditional direct-drive diesel engines, only one of the tugboat's two engines needs to operate, halving engine uptime. Simultaneously, the engines avoid prolonged low-speed, low-load operation, extending engine overhaul cycles by more than double, reducing fuel consumption and equipment maintenance costs. Under low loads, the electric motor drive allows for stepless speed regulation of the propeller from zero, improving the tugboat's maneuverability when berthing and unberthing. Compared to conventional hybrid and pure electric propulsion systems, it eliminates the need for high-power generators and drive motors. These generators and drive motors are smaller, smaller, and less expensive, making them suitable for retrofitting traditional tugboats.

[0022] The P1 generator includes a left P1 generator and a right P1 generator. One end of the input shaft of the left P1 generator is connected to one side of the engine output shaft via gear meshing, and one end of the input shaft of the right P1 generator is connected to one side of the engine output shaft via gear meshing.

[0023] The P2 motor includes a left P2 motor and a right P2 motor. One end of the output shaft of the left P2 motor is connected to one end of the output shaft of the gearbox through gear meshing, and one end of the output shaft of the right P2 motor is connected to one end of the output shaft of the gearbox through gear meshing.

[0024] This includes three modes: pure electric power, hybrid power, and direct drive. Through a switching control algorithm, the ship's operator can seamlessly switch between these three modes with a single button using the same throttle control lever in the wheelhouse. The specific solution is as follows:

[0025] In the pure electric power mode, power is drawn from the DC grid to drive the output shafts of the left and right P2 motors, which in turn drive the Z-type propellers. In pure electric propulsion mode, under conditions of anchoring, waiting for work, and low load (single unit power < 400 kW), the power lithium battery pack directly supplies power to the DC grid to drive the P2 motors, with the output speed arbitrarily set from 0 rpm to 520 rpm. At this time, the tugboat's still water speed can reach 11 knots. The operating time of the pure electric propulsion mode under lower loads is determined by the capacity of the power lithium battery pack.

[0026] In the direct drive mode, the engine output shaft drives the gearbox input shaft to rotate, and the gearbox output shaft drives the Z-type propeller to rotate. In direct drive mode, during long-haul towing, high-speed cruising, or situations requiring high-power towing (single engine power > 400KW), both engines start, the gearbox clutch engages, and the engines directly drive the Z-type propeller. Simultaneously, the surplus power of the engines drives the P1 generator to generate electricity to the DC grid, supplying power to the ship's electrical system and replenishing the battery pack. If the tugboat needs to accelerate, the P2 motor operates briefly, with both the engine and P2 motor working together, effectively solving the problem of black smoke caused by sudden load changes during conventional power tugboat operations. When the operating load is low, the tugboat automatically exits direct drive mode and switches to hybrid or pure electric mode.

[0027] In the hybrid mode, starting the engine drives the output shaft to power the left and right P1 generators, which in turn supply power to the left and right P2 motors. Excess energy is used to charge the battery pack. In hybrid mode, when the lithium battery pack is low and the tractor is under low load (single engine power < 400KW), one of the two engines automatically starts, driving the P1 generator to supply power to the left and right P2 motors. Excess energy is used to charge the battery pack.

[0028] The inverter is a three-phase AC inverter, which is used to convert the DC power from the DC grid into three-phase AC power, and connect to the ship's power grid to provide power for the tugboat's navigation, control, winch, and lighting auxiliary equipment.

[0029] The system has two engines, one of which serves as the main generator set and the other as a direct drive unit. The rated power of generator P1 is 50%-60% of the rated power of the engine, and the maximum power of motor P2 is 50%-60% of the rated power of the engine. In hybrid mode, one generator can simultaneously meet the normal power requirements of two drive motors.

[0030] Taking a 4000-horsepower port tugboat as an example, the rated power of the diesel engine is 1470KW; the power of generator P1 is 800KW; the common power of motor P2 is 400KW, and the maximum power is twice the common power.

[0031] The battery pack is a lithium-ion battery pack. It is equipped with a wide range of lithium battery capacities. With a battery pack of a certain capacity, in pure electric mode, the maximum operating range at the port can reach 2-3 hours. After operation, it can be recharged via shore power, achieving zero fuel consumption and zero emissions, thus meeting the requirements for energy conservation and emission reduction.

[0032] This invention utilizes an engine and a P1 generator. In hybrid mode, the P2 motor is powered while the battery pack is charged. In direct-drive mode, the engine's surplus power supplies the DC grid, and the battery pack provides additional power. The P2 motor drives the Z-shaped propeller in both pure electric and hybrid modes. In direct-drive mode, when the tugboat needs acceleration, the engine and motor work together, effectively solving the problem of black smoke caused by sudden load changes during conventional tugboat operations. Compared to conventional hybrid and pure electric propulsion systems, this system eliminates the need for high-power generators and drive motors. The generators and drive motors are smaller, smaller, and less expensive, making it suitable for replacing and retrofitting traditional tugboats. This system is designed for the characteristics of port tugboat operations. Under low load conditions, in pure electric or series hybrid mode, only one diesel engine is needed as the main generator set for intermittent operation. Under medium and high load conditions, the diesel engine's direct-drive mode offers high transmission efficiency and low energy conversion loss, allowing the engine to operate continuously in a highly efficient and fuel-efficient manner, reducing fuel consumption.

[0033] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A harbour tug hybrid power system comprising an engine and a Z-drive propeller, characterised in that: The engine power output end is connected with a gear box, the gear box is provided with a clutch, the gear box output shaft one end is connected with a Z-shaped propeller, the engine output shaft one side is provided with a P1 generator, the gear box output shaft one end is provided with a P2 motor, the P1 generator is electrically connected with a direct current network, the direct current network is electrically connected with a battery pack and an inverter, the inverter is electrically connected with a ship power grid, and the ship power grid is electrically connected with the P2 motor. The P1 generator includes a left machine P1 generator and a right machine P1 generator, the left machine P1 generator input shaft one end is connected with the engine output shaft one side through gear engagement, and the right machine P1 generator input shaft one end is connected with the engine output shaft one side through gear engagement. The engine has two, one of which is used as a main generator set, and the other is used as a direct drive power set, the rated power of the P1 generator is 50%-60% of the rated power of the engine, and the maximum power of the P2 motor is 50%-60% of the rated power of the engine. The battery pack is a lithium ion battery pack. The P2 motor includes a left machine P2 motor and a right machine P2 motor, the left machine P2 motor output shaft one end is connected with the gear box output shaft one end through gear engagement, and the right machine P2 motor output shaft one end is connected with the gear box output shaft one end through gear engagement.

2. The hybrid power system for port tugboats according to claim 1, characterized in that: The inverter is a three-phase alternating current inverter, which is used for converting direct current of the direct current network into three-phase alternating current, and providing power for the tugboat navigation, control, winch, lighting auxiliary equipment in the ship power grid.

3. The hybrid power system for port tugboats according to claim 1, characterized in that: The battery pack is a lithium ion battery pack.

4. The hybrid system of claim 1, wherein: The battery pack is a lithium ion battery pack.

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